Model Answer
0 min readIntroduction
Groundnut (Arachis hypogaea L.) is a crucial oilseed crop in India, contributing significantly to the country’s edible oil production and providing a vital source of protein. However, its productivity is often hampered by various biotic stresses, among which Tikka disease, caused by *Cercospora arachidicola*, is the most devastating. First reported in India in 1909, Tikka disease can cause yield losses ranging from 50% to 70% under severe epidemic conditions, impacting the livelihoods of millions of farmers. Understanding the disease’s biology and effective management strategies is therefore paramount for ensuring sustainable groundnut production.
Understanding Tikka Disease
Tikka disease is a fungal disease affecting all parts of the groundnut plant, but is most prominent on the leaves. It is characterized by the appearance of small, circular, reddish-brown spots that gradually enlarge and develop concentric rings, giving them a ‘bull’s eye’ appearance. The disease is favored by warm, humid weather and continuous rainfall.
Causal Organism and Disease Cycle
The causal organism, *Cercospora arachidicola*, is an ascomycete fungus. The disease cycle involves the following stages:
- Primary Infection: Occurs through conidia (asexual spores) carried by wind and rain from infected plant debris left from the previous season.
- Incubation: After landing on susceptible leaves, conidia germinate and penetrate the leaf tissue.
- Secondary Infection: The fungus produces numerous conidia on the lesions, leading to rapid spread during favorable conditions.
- Survival: The fungus survives in the soil and on infected plant debris as mycelium.
Symptoms of Tikka Disease
The symptoms of Tikka disease vary depending on the stage of infection and the plant part affected:
- Leaf Spots: Small, circular, reddish-brown spots with concentric rings.
- Stem Blight: Dark, sunken lesions on the stem, leading to girdling and plant death.
- Pod Infection: Small, dark spots on the pods, reducing seed quality and yield.
- Defoliation: Severe infection leads to premature defoliation, reducing photosynthetic area and ultimately impacting pod filling.
Favorable Conditions for Disease Development
Several environmental factors contribute to the development and spread of Tikka disease:
- Temperature: 25-30°C is optimal for fungal growth and spore germination.
- Humidity: High relative humidity (above 70%) favors spore production and infection.
- Rainfall: Frequent and prolonged rainfall facilitates spore dispersal and infection.
- Wind: Wind aids in the spread of conidia over long distances.
- Close Planting: High plant density reduces air circulation and increases humidity within the canopy.
Management Strategies
Effective management of Tikka disease requires an integrated approach:
- Cultural Practices:
- Crop rotation with non-host crops like cereals and pulses.
- Deep ploughing to bury infected plant debris.
- Proper spacing to ensure adequate air circulation.
- Avoiding overhead irrigation.
- Chemical Control:
- Prophylactic spraying of protectant fungicides like Mancozeb (2.5 g/L) or Chlorothalonil (2 g/L) at 20-25 days after sowing and repeat at 40-45 days.
- Systemic fungicides like Propiconazole (1 ml/L) or Hexaconazole (1 ml/L) can be used in severe cases.
- Biological Control:
- Use of *Trichoderma* species as a bio-control agent.
- Application of bio-fungicides containing *Bacillus subtilis*.
- Resistant Varieties:
- Development and cultivation of Tikka-resistant groundnut varieties like JL-24, ICGV-91114, and TG-37A.
- Integrated Nutrient Management: Balanced fertilization enhances plant vigor and resistance to diseases.
Recent Advancements
Recent research focuses on developing groundnut varieties with enhanced resistance to Tikka disease through marker-assisted selection and genetic engineering. Furthermore, the use of nanotechnology for targeted delivery of fungicides is being explored to reduce environmental impact and enhance efficacy.
Conclusion
Tikka disease remains a significant threat to groundnut production in India. A comprehensive and integrated disease management approach, combining cultural practices, chemical control, biological control, and the use of resistant varieties, is crucial for minimizing yield losses and ensuring sustainable groundnut cultivation. Continued research and development of novel management strategies are essential to address the evolving challenges posed by this devastating disease.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.